GH cells are clonal strains of rat pituitary cells that can be serially propagated in culture indefinitely and that perform many of the differentiated functions of normal somatotrophs and lactotrophs in situ, in other words, they secrete authentic rat growth hormone and prolactin and respond to many of the regulatory signals that control the biosynthesis and secretion of these two protein hormones. Because of their ease of growth, ready availability, high rates of specific hormone production and response to regulatory factors, these cell strains have become widely used in the last several years for mechanistic studies which could not be performed in heterogeneous primary cultures, in whole pituitary glands, or in intact animals. These investigations have been particularly informative in the areas of molecular biology (isolation, characterization and regulation of the genes for GH and PRL), cell biology (ultrastructural studies on hormone packaging and secretion; hormone receptor characterization and transduction; roles of phosphoinositide metabolism, intracellular Ca2+, and protein phosphorylation in regulation GH and PRL synthesis and release), and biophysics (electrophysiology of secretory cells, voltage-dependent and voltage-independent Ca2+ channels). In the last year, the interrelationships between the molecular biology, cell biology, and neurobiology of GH cells has become clear, and yet the leading researchers in the separate areas have never convened at a common site to share their most current insights and knowledge. The purpose of this Workshop/Conference is, therefore, to bring together a group of the most active scientists working on GH cells and several of the premier researchers in the major relevant disciplines to exchange knowledge of their latest findings and techniques, and to enable contemporary methodology to be used to solve several of the principal unsolved molecular problems in physiology (e.g. hormonal regulation of specific gene expression, role of intracellular Ca2+ in protein secretion, and ligand regulation of specific ion channels).